Why are JPEG images from camera huge and the same images exported from Vistaprint software 10 times smaller?

Question

JPEG images from my Nikon D3300 are roughly 12-15MB big at 6000 x 4000resolution. RAW images converted to JPEG through LightRoom are also 12-16 MB. I recently created an album through VistaPrint software, upon exporting I found that it compresses images and saves it to a folder before uploading it to VistaPrint server.

16MB image was reduced to mere 1.2-2 MB maintaing the resolution and image quality. I could not find any quality difference between the two. Now I am wondering it its really worth storing images at 12-18MB size on my HDD? I considering exporting all my images through VistaPrint software and storing those instead of the original JPEGs.

Answer 1

Without going into a detailed explanation of JPEG, it is (in general) a lossy format: if you save a file as JPEG and then load it again, some of the pixels will have changed. However, unless you know what to look for you may not notice the changes. Moreover, there is flexibility as to how much information is thrown away: the more you lose, the smaller the file, but the more likely that the differences will be noticeable.

Your Nikon D3300 has three levels of JPEG quality (= compression): basic, medium, and fine. I suspect that if you adjust it to use basic JPEG then the result will be files of about 2-3MB instead of 12-15MB. (This is off the top of my head, based on what I observe on my D5300, which has the same sensor size).

However, dedicated image processing software has many more levels. It's not unusual for software to offer 100 different levels of compression (= quality). If you use the GIMP then when you save as JPEG you can adjust a quality slider and view in real time the results of the compression and the size of the file it will produce.

What I do personally is to save everything in RAW + Basic JPEG; I use the JPEGs as full-size "thumbnails" to decide which RAW files to process into high-quality JPEGs using Darktable. From memory, I think that I have Darktable configured to export at quality 98 of 100. Typically it produces files about 5MB, but the size obviously depends on how tightly I crop as well as the complexity of the scene. I would be surprised if Lightroom doesn't have a similar setting somewhere.

Factors to take into account:

• Whenever you load a JPEG, edit something, and save as JPEG you apply a cumulative lossy compression. There are certain changes to a JPEG which can be made without increasing the information loss, but they are limited to cropping at certain points in the image, flipping or rotating by multiples of 90 degrees, and certain colour transforms; and they require specialised software. Therefore if you only store compressed JPEGs you are effectively committing yourself to not making future edits.
• Whether it is "worth" storing a larger file depends on whether you have an SSD or a spinning rust drive (i.e. how much it costs per MB) and how many photos you take. I personally have taken on the order of 70000 photos in the past two years and am still a long way from filling my disk drive, so in my situation there's no real reason not to keep the RAW files as well as the processed JPEGs. If I get short on space then the first thing I can do is to delete the basic JPEGs, but for the time being that doesn't worry me.

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TL;DR

• You can get smaller files directly out of the camera by setting it to save in Basic or Medium quality JPEG.
• You can get better control of the quality/file size tradeoff using image editing software. Lightroom probably supports this.
• Which format to keep for long-term storage is a tradeoff: we can give you pros and cons, but the decision of which are more important is yours.

Answer 2

JPEG is a lossy format, some information in the original image will be lost when saving as a JPEG. By choosing different settings when performing the JPEG compression you can trade off image quality for file size. Most software presents the user with a single "quality" setting which is used to determine the parameters to use for the JPEG compression.

The relationship between filesize and perceived image quality is highly nonlinear. As you get towards the top of the quality range the filesize increases dramatically but in most cases there is little impact on the perceived quality of the image.

There can also be slight changes caused by the choice of arithmetic or huffman coding. Arithmetic coding gives slightly smaller filesizes for the same quality but not all decoders can read it (historically it had patent issues, AIUI the patents have now expired but still not all software has updated it's decoder libraries).

You should try out different quality settings in lightroom and/or your camera, I expect you will see a similar case of dramatic reductions in filesize without immediately noticable changes in quality.

Having said that you should also remember that once you throw something away you have thrown it away and that just because quality loss is not immediately apparent doesn't nessacerally mean it is not there. For example a lower JPEG quality may destroy shadow details that is not readilly visible to the naked eye but can be brought out through retouching techniques. This is especially a concern when doing JPEG in-camera, it's much less of a concern when you are using RAW files for capture and archival and only using JPEG as an output format.